Fermentation parameters such as moisture content, the amount of soluble carbohydrates, protein and fiber contents of the initial forage, microbial populations and the amount of oxygen that starts the fermentation, pH, smell, Fleig's score, and aerobic stability must be considered. Among these, aerobic stability is the most important criteria that affect the silage quality and feeding value of silage after fermentation is complete. Especially after the silage is exposed to oxygen during feed out phase, it is the ability of silage to resist to unwanted microbial growth. Aerobic stability method is based upon the principle of temperature change (rise) of the material when the silage is exposed to oxygen. Moisture content and chemical compositions of the silages affect the quality closely. Especially silage with high moisture and protein contents cause butyric and ethanol rich fermentations frequently. Silage pH is another factor needs to be considered. Especially for corn and sugar beet pulp silages have the pH values of 3.5-4.0 due to their high-water soluble carbohydrate concentrations, while legume silage has the pH higher.